Try rowing or cross-country skiing instead of running. Much easier on the knees. It'll probably help your joints.

I'm a competitive ultimate player, and I really like my sport. I'm just saying, excercise like everything else is not an unalloyed good. My achy knees today after practice yesterday are evidence.

The right kind of exercise helps a lot. Ultimate as a sole source of exercise is clearly not the right kind (though it's probably much more enjoyable).

Oh definitely! I train all the time, I try to do 4 nights a week. I'm better at it in the offseason than I am during the season, because my body gets beat up and it's hard to convince myself to train when I'm sore.

It's just that ultimate is so stressful to my body that it overwhelms the rest of what I do.

I'm glad to talk your ear off about training methods, crossfit and tabatas, but this is probably not the right place for it. DIY gyms are kind of hacker though.

Pilates and biking are my two favorite forms of exercise.

The problem with running is that by the time you realize you're too out of shape to run, it's too far to walk back. (re-joke)

Do anything that doesn't involve impact on those joints.